The present invention relates to a method of manufacturing semiconductor devices, more particularly to a method of making a pattern of tungsten (W) film which is used for metal interconnection.
On semiconductor substrate, many devices are formed through various manufacturing processes and metal films are used to interconnect these devices to each other. The metal interconnection is achieved through photomasking and metal etching processes after deposition of the thin metal film of mostly 1.0-1.5 .mu.m.
Presently, aluminum (Al) containing silicon (Si) at the proper ratio is widely used as the metal material in the semiconductor manufacturing processes. When the aluminum is used for the metal interconnection, however, the aluminum film is thinned by electromigration phenomenon and in the worst case the aluminum film is disconnected, thereby bring about no operation of the semiconductor devices.
Particularly, as the semiconductor devices become more and more high-integrated, such a problem often occurs since the metal interconnect films are more thinned.
In order to prevent the thinning of the metal interconnect films due to the electromigration phenomenon, tungsten (W) with a large atomic radius and heavy mass is used as the metal interconnect material. Also, the operation speed of the semiconductor devices is improved due to a low ohmic resistivity of tungsten and for a long time it can be reliable. But, since the conventional method of forming the tungsten interconnect pattern employed the etch back process as shown in FIG. 1, the surface of the semiconductor devices is rough, thereby leading to many difficulties at the next processes.
To investigate this process in detail, a first insulating layer 2 is first formed on a substrate 1 and doped. Next, a second insulating film 3 is deposited by the chemical vapor deposition (CVD) technology, and the pattern for the deposition of tungsten 5 is formed through the photomasking and etching processes. After an adhesive material 4 is deposited over the pattern to improve the adhesion of the tungsten the tungsten 5 is grown by selective CVD technology. Subsequently, in order to remove the dot-line portion in FIG. 1, the etch back process is carried out, thereby becoming the shown in FIG. 1.
If the tungsten interconnection is formed by this method, voids 6 are produced due to the step coverage of the tungsten and the surface of the insulating film 3 becomes very rough during the etch back process, and a residual 7 of the tungsten remains on the insulating film 3. Accordingly, there occurs the problem that the short phenomenon between the tungsten interconnect lines is brought about due to the residual 7 of the tungsten in the next processes.